The axp20x driver assumes the device is i2c based. This is not thecase with later chips, which use a proprietary 2 wire serial busby Allwinner called "Reduced Serial Bus".

This patch follows the example of mfd/wm831x and splits it intoan interface independent core, and an i2c specific glue layer.MFD_AXP20X and the new MFD_AXP20X_I2C are changed to tristatesymbols, allowing the driver to be built as modules.